1. Field of the Invention
The present invention is generally related to deployable structural assemblies and, more particularly, to generally elongated, deployable structural assemblies having a high strength and stiffness to weight ratio that are highly compact for storage purposes, are efficiently deployed and retracted and are suitable for numerous uses.
2. State of the Art
It is often desirable to utilize a deployable structural assembly in various circumstances and environments. For example, deployable structural assemblies, sometimes referred to as deployable booms, may be utilized in conjunction with satellites or other aerospace vehicles. In many instances, the rigors of launching a satellite or aerospace vehicle make it impractical to have a structural assembly in an already deployed condition or as a permanent installation such that it is extending or protruding from the vehicle during launch. Thus, it is often desirable to delay the deployment of a structural assembly until it is needed for a specific purpose.
Even after an aerospace vehicle has been placed in a stable flight pattern or in orbit, it may not be desirable to continually maintain a structural assembly in a deployed state. Thus, it becomes desirable to utilize a structural assembly that is capable of being deployed and retracted, relative to the satellite or aerospace vehicle, when desired or on demand Such a structural assembly may be utilized to deploy, for example, solar sails or solar shields in association with a satellite after the satellite is placed in orbit. Deployable structural assemblies may also be used, for example, as an aid to an astronaut during maintenance activities when the astronaut is required to leave his or her aerospace vehicle to perform a specified activity, such as during the repair of a satellite or another aerospace vehicle.
Of course deployable structural assemblies have utilization in other circumstances as well including, generally, situations where it would be inefficient to build a permanent structural assembly but where a structural member or assembly is required to provide additional height or to span a distance in order to support or place a given component or structure at a specified location. In one example, a deployable structural assembly may be used to position a bank of lights above a specified area such as in an emergency situation or in association with an outdoor concert or other activity. Similarly, a deployable structural assembly might be used to position an antenna or other communications device. In another example, one or more deployable structural assemblies may be used to support a raised platform, which may serve as a working surface for one or more people.
Numerous configurations of deployable structural assemblies have been developed. For example, U.S. Pat. No. 2,130,993 issued to Dubilier; U.S. Pat. No. 2,799,368 issued to Alter; U.S. Pat. No. 3,213,573 issued to Bohr et al.; U.S. Pat. No. 3,503,164 issued to Berry et al.; U.S. Pat. No. 4,027,440 to Hamblin; and U.S. Pat. Nos. 4,386,485 and 4,651,480 issued to Kramer, each disclose deployable structural assemblies.
The Dubilier patent discloses a three-sided collapsible rod wherein the side components are made of sheets of flexible steel. The collapsible rod is stated to be used for deploying an antenna or as a rail component of a ladder.
The Alter patent discloses a four-sided collapsible structure that is formed of steel side sheets and which may also be used in conjunction with the temporary deployment of antennas.
The Bohr patent discloses a three-sided collapsible structure that may be used for supporting aerial masts or derrick booms. The structure is formed by engaging alternating teeth located at the edges of adjacent side elements in a zipper-like manner.
The Berry patent discloses a tubular structure having two interlocked sheets of material that are rolled flat during storage, but that expand due to stored energy when they are unrolled.
The Hamblin patent discloses an extensible structure used for tower cranes and scaffolding towers. The structure includes a plurality of modular truss-like structures that are hingedly coupled such that each module may be folded and stacked relative to one another.
The Kramer patents disclose extendible structures formed of flexible side sheets having locking members that each include a hemispherical projection at one longitudinal end thereof and a hemispherical recess at the opposing longitudinal end thereof. The locking members of adjacent side sheets are fastened together in an alternating zipper-like fashion such that the hemispherical projection of one locking member engages with the hemispherical recess of an adjacent alternating locking member. In one of the Kramer patents, the locking members are formed in the side sheet, while in the other patent, the locking members are formed as a part of a stiffening member.
While the above-listed U.S. patents show various configurations of deployable structural assemblies, it is desirable to improve upon the deployable structural assemblies disclosed in the prior art with regard to various features. For example, it is desirable to provide a deployable structural assembly having an improved interlocking arrangement that will enhance the integrity of the structure when deployed, while also providing efficient, simplified and reliable deployment and retraction. Additionally, it is desirable to provide a deployable structural assembly with an improved strength and stiffness to weight ratio while also being scalable in design such that various lengths, cross-sectional sizes and load capacities may be provided. It is also desirable to provide a deployable structural assembly that provides a significant reduction in stowed size and an improved packing factor as defined hereinbelow.